Abstract
Halophytes are unique in that they can thrive in a wide range of soil conditions, from normal to extremely saline. This has recently prompted researchers to consider using halophytes as a phytoremediation end-product as a source for biogas generation. Therefore, applying the anaerobic digestion process for halophytes may have the potential advantage in terms of efficient land utilization, soil remediation, and biogas production. Based on this, the anaerobic digestion efficiency of high saline biomass was investigated in continuous laboratory-scale anaerobic reactors at two different sludge residence times (SRT) of 40 and 80 days. Under mesophilic atmosphere, two reactors were operated, one reactor used organic substrate with 30 g-Na+.L-1 originating from sodium chloride whereas the other was operated with the presence of sodium bicarbonate and sodium sulfate. The salt-tolerant microorganism was gradually developed and the salt concentrations were selected based on the elemental analyses results of 30 species of wild halophyte plants taken from the saline-affected area of the Aral Sea in Uzbekistan during the early phase of the operation. For 40 and 80 days of SRT, respectively, 65.56 percent and 60.42 percent of the feed COD were converted into methane gas by the chloride system. However, only about 60% of the feed COD was converted into methane for bicarbonate, and the remaining fraction of gas was assigned to sulfide as a final product of increased sulfate reduction bacteria activity. These findings showed that the salt-tolerant microorganism could be incubated and the anaerobic digestion process could be adapted for a high-saline substrate, implying that the biodegradability of phytoremediation end-products may be used for methane production.
Highlights
Because of urbanization and the increasing worldwide population, arable land is decreasing
In terms of the efficiency of anaerobic digestion process- g-Na+.L-1 eventually has no impact on the bioconversion es, more than 60% of the feed substrate was converted to a anymore after a long-term operation, suggesting a successful gas phase which 0means20it is p4o0ssibTlei6m0teo(Dgaey8t)0high1m00etha1n2e0 gradual adaptation to higher sodium concentrations
This study focused on the anaerobic digestion performance under high saline conditions
Summary
Because of urbanization and the increasing worldwide population, arable land is decreasing. Soil salinity is one of the most serious environmental factors limiting agricultural crop productivity and the quality of crops. Because most ordinary crops are salt sensitive, salinity affects a large percentage of agricultural fields, making conventional agriculture ineffective. Several practical measures, including soil washing and irrigation control, are being used to restore the affected lands (Toderich et al 2009). A biological engineering solution called phytoremediation using halophyte plants is a promising approach to reform the salinized lands. Halophytes are distinguished as they can flourish well in soils ranging from normal to severely saline conditions and it can offer an interesting alternative feedstock for the process of biogas production. Anaerobic digestion of residual phytoremediated biomass provides the ability to produce methane which can be used as electrical and thermal energy
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